Leak from rear of transmission. Pan Gasket?

[Steve190E 2.3]

My 1988 300E has a leak that is quite possibly from the tranny pan gasket. I had the tranny out to replace the front pump seals, and at that time I removed the pan to replace the filter. I had just put the used tranny in about a week before and found that there was a leak around the front pump. I also noticed that there was a leak near the rear of the transmission. I checked the gasket which was brandnew when I replaced the tranny and it looked perfect. I finished putting it all back together and it is still leaking. How can I find out exactly where it is coming from? Also, if the pan gasket looks fine, how could it leak? Is it possible that the pan is bent and not sealing even though it looks perfect? Sorry about all the questions. BTW I don't know what I would do without this site.